1. Field of the Invention
The present invention relates generally to energy converters and more particularly to an energy converter which utilizes a regenerative gas cycle and an oscillatory gas flow through the regenerator.
2. Description of the Prior Art
Various energy converters have been previously disclosed utilizing a modified Stirling cycle and a free or semi-free piston which alternately displaces gas back and forth between a hot space (a hot chamber) and cold space (a cold chamber) via a thermal regenerator as the piston oscillates in a cylinder. The temperature difference between the hot and cold chambers is maintained by means of a heating means or chamber and a cooling means or chamber and this alternate displacement of gas causes an alternate heating and cooling of the gas by the heating and cooling chambers and by the regenerator connecting these two chambers. This alternate heating and cooling results in a cyclical variation or modulation of the gas pressure. This modulated pressure may in turn be used to drive a load, such as a working piston, which may also be a free piston and which typically oscillates up to about 90.degree. out of phase with respect to the displacer piston, and the oscillating working piston may do mechanical, pneumatic, or electro-magnetic work. The displacing and working pistons may also be combined so as to form a single complex piston having a displacing piston mounted on a working piston and moving relative to the working piston to accomplish its function. Or, the displacing piston may be porous and act as an oscillating regenerator to accomplish its function.
The modulated pressure energy developed by means of the displacing or working piston can be used for fluid pumping purposes by means of check valves which rectify the modulated pressure, or, as described within my copending application, Ser. No. 502,748, filed Sept. 3, 1974, now U.S. Pat. No. 3,973,771 entitled Illusion Amusement Device and as also described and illustrated herein, a pressure driven load, such as for example, a turbine, may be driven directly by such a device without the use of check valves, by means of the pressure modulated fluid of such a device issuing from a nozzle which directs the reciprocating fluid against the load.
I have previously invented a free piston, Stirling type device such as described above and various embodiments of this device are described and illustrated within my U.S. Pat. Nos. 3,782,859, entitled "Free Piston Apparatus, " and 3,767,325, entitled "Free Piston Pump." The free piston of this device can be of simple and integral construction, and it is a completely free piston. The piston is reversed by means of a gaseous spring, which does not wear out, as compared with a mechanical spring, and the means for reversing the direction of motion of the free piston, twice each cycle, is relatively independent of the load, whereby the device is essentially stall-free. Since the free piston is guided by means of the cylinder itself, there is no need for a separate guidance apparatus or for accurate alignment of such a guidance apparatus with the cylinder. In addition, in the simplest form of my device, the single free piston is the only moving part required for developing the cyclical pressure variation. To my knowledge, none of the other Stirling-type free piston energy converters have all of these advantages features.
However, my approach to this family of devices appears to have a slight disadvantage which most, if not all, of the other devices do not have. In one of its simplest forms, my device has a single heating chamber. The sole heating chamber, in contrast with the other devices, serves as a thermal lag heating chamber for driving the free piston and, also in contrast with these other devices, the sole heating chamber is not located in the cylinder bypass, where it would each cycle heat substantially all of the gas forced from the cold chamber to the hot chamber via the bypass. Instead, the sole heating chamber is disposed outside of the bypass and communicates with the hot end of the cylinder by means of a separate heating chamber port which is located beyond the bypass. The heating chamber port is located in or very near the hot end-wall of the cylinder, whereby the heating chamber communicates with the hot end of the cylinder while the hot bypass port is blocked by the piston side-wall during the hot rebound portion of the cycle, during which portion of the cycle the heating chamber functions not only as part of the hot rebound chamber but also as a thermal lag heating chamber for sustaining piston oscillation (see my U.S. Pat. No. 3,807,904, entitled "Oscillating Piston Apparatus," for a relatively thorough description of a thermal lag heating chamber; my U.S. Pat. No. Re. 27,740, entitled "Oscillating Free Piston Pump," also discusses thermal lag heating).
The heating of the gas forced by the piston into the heating chamber during this hot rebound portion of the cycle, in addition to the heating of the gas forced into the heating chamber during the next portion of the cycle as a result of the increasing pressure in the cylinder while the piston coasts within the bypass region in a direction away from the hot cylinder end, combine to essentially provide the cyclical heating by the heating chamber of gas forced from the cold chamber to the hot chamber via the regenerator in the bypass. While it is normally desirable for all of the gas being forced through the regenerator to be heated by the heating chamber each cycle, and while this goal is apparently substantially accomplished by the other Stirling type devices of which I am aware, it is difficult to say, in the case of my device, just how much of this forced gas enters the sole heating chamber of my simplified device each cycle during the above two portions of my cycle. Certainly a substantial amount of such gas does enter my heating chamber for heating therein such cycle; however, this amount may well be substantially less than 100% of such gas, the main problem occurring during the above-mentioned coasting portion of the cycle while the piston iscoasting in the bypass region in a direction away from the hot end of the cylinder (toward the cold end of the cylinder) primarily because the bypass flow is not angled toward the heating chamber. Although the advantages of my approach, discussed first, may out-weigh this slight disadvantage, discussed last, it nevertheless is the prime object of the present invention to correct this slight deficiency without introducing any new deficiency.